Brain Fog!??

This is my first time using this site, so I'm hoping I am posting the following question in the right place :)

I am curious if anyone has had, or has heard of something which I call "Brain Fog".

I have been experiencing a lot of brain fog lately. It usually starts as soon as I wake up after a long nights sleep. (Today, I had 12 hours sleep).

I'm experiencing confusion, lack of concentration, inability to think for long periods of time, blurred (foggy) vision. I feel as if I'm a zombie and feel like I just "havent woken up". I've been awake for 4 hours now, but it hasn't been getting any better. I feel like I'm on auto-pilot. :(

I have experienced this before and usually I just go back to sleep because of the frustration is causes. It's a really scary feeling, as I can't do too much. I feel overly fatigued. I dont even know how much sense I am making right now. So I hope someone understands and can give me some sort of idea as to what it going on with me.

I know that for most people if you sleep too long you can wake up feeling "groggy". But shouldnt that go away sooner than with what Im experiencing? I'm pretty sure I am going to feel like this all day/night. And to me, it doesn't sound like a "common" over-sleeping problem.

My History:Suffering from Depression for the past 12 years. " " Anxiety disorder for 12 years." " Night terrors for most of my life.